Code
B143D
LAND ROVER
B — Body
Air suspension compressor - Power supply
Views:
UK: 2
EN: 6
RU: 3
AI status
Completed
Completed
100%
Causes
- Blown fuse or faulty fuseholder for compressor supply
- Faulty compressor relay or relay socket
- Damaged wiring harness or chafed/shorted wires to compressor
- Corroded or loose connector at the compressor
- Failed compressor motor (open or internal short)
- Poor chassis ground or connector ground fault
Symptoms
- Air suspension warning message or lamp on dash
- Compressor does not run when system requests inflation
- Vehicle ride height low/sagging; inability to raise vehicle
- Compressor runs intermittently or not at full speed
- Excessive cranking or repeated compressor attempts
- Battery drain or repeated low-voltage events while attempting to run compressor
What to check
- Read and record all stored DTCs and freeze-frame/conditions
- Visual inspection of fuses and fuseholder for the air suspension circuit
- Inspect compressor relay and swap with known-good relay if available
- Inspect wiring and connector at the compressor for corrosion, damage or water
- Check battery condition and terminal connections (voltage and cranking)
- Measure voltage at the compressor power and ground terminals with key on and during commanded run
Signal parameters
- Supply voltage at compressor power pin (key on): approximately battery voltage, typically 11–14.5 V
- Voltage at compressor while commanded to run: should remain near battery voltage (allowing small drop under load)
- Control signal: on/off or PWM from suspension module (0–12 V or 0–100% duty cycle depending on design)
- Ground resistance: low, typically
- Compressor current draw: measured running current normally within manufacturer range (typical running: ~5–20 A; higher inrush possible on start)
- Compressor motor winding resistance: small value (manufacturer spec) — open circuit indicates failed motor
Diagnostic algorithm
- Record codes and freeze frame. Clear codes and perform a key cycle to see if fault returns.
- Verify battery voltage (resting and while cranking). Recharge or replace battery if low and retest.
- Perform visual inspection of fuse(s) and relay(s) in the air suspension power circuit. Replace any blown fuses and retest.
- Inspect the compressor connector and wiring for corrosion, damaged insulation, pin push-out, or water ingress. Repair any damage and apply dielectric grease.
- With connector connected, backprobe the power and ground pins. Verify battery voltage at the power pin with key on and module requests. Verify solid ground.
- Command compressor on using a diagnostic tool while monitoring voltage at the connector. Observe voltage drop and listen for compressor operation.
- Measure in-line current during compressor activation. Excessive current suggests mechanical seizure or internal motor short; near-zero current suggests open circuit or relay fault.
- If supply voltage and ground are correct but compressor does not run, disconnect connector and measure motor winding resistance. An open or shorted winding indicates motor replacement.
- If compressor supply is intermittent or absent at the connector while commanded, check relay coil activation and control module output. Test relay socket and wiring continuity to fuse and battery.
- Check ground continuity from compressor ground to vehicle chassis; repair poor grounds.
- If wiring and compressor are good but fault persists, test/replace relay and consider replacement or reprogramming of the suspension/body control module per manufacturer guidance.
- After repairs, clear codes and perform system relearn/height calibrations if required. Verify normal operation and no return of the DTC.
Likely causes
- Blown fuse or faulty relay supplying compressor (most common)
- Damaged connector/wiring at the compressor (water ingress/corrosion)
- Compressor motor failure (open circuit or excessive current draw)
- Poor ground connection at compressor or chassis
- Faulty module output (less common) or intermittent wiring fault
Fault status
Status
Power supply fault detected for air suspension compressor — circuit voltage out of range, open, or short. Compressor may not operate correctly until supply/ground, wiring, relay, or compressor is repaired.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
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